Safety appliance for electrically heated apparatus



y 1942- A. E. LANIGAN 2,

SAFETY APPLIANCE FOR ELECTRICALLY HEATED APPARATUS Filed Oct. 31, 1938 2Sheets-Sheet 1 ALFRED 5 LAN/@AW May 5, 1942. A. E. LANIGAN SAFETYAPPLIANCE FOR ELECTRICALLY HEATED APPARATUS 2 Sheets-Sheet 2 .ALFRED ELAN/GAN Filed Oct. 31, 1938 ,uuuuu l l Illll Patented May 5, 1942 UNITEDSTATES PATENT OFFICE SAFETY APPLIANCE FOR ELECTRICALLY HEATED APPARATUSAlfred E. Lanigan, Ferndaie, Mich, assignor to Electromaster, Inc.,Detroit, Mich, a corporation of Michigan 3 Claims.

The present invention relates in general to safety appliances or devicesof the type wherein means are provided for automatically interrupting anelectrical circuit upon the occurrence of abnormal operatingtemperatures, and is particularly concerned with such devices as may beutilized for protecting electrically heated cooking and heatingapparatus, such as electric tea kettles, percolators, and the like.

The invention as used with such apparatus contemplates an arrangement inwhich the electrical connection will be maintained. so long as theapparatus contains a liquid, but will immediately operate toautomatically disconnect the electrical connection in the event that theliquid evaporates to such an extent as to subject the apparatus topossible damage by becoming overheated.

It is a further object of the invention to provide an improved safetyappliance which is latched against operation at normal temperatures, butwhich will be unlatched for operation at abnormal temperatures, andwhich includes a novel and improved resetting mechanism for the latch.

While the invention will be described in connection with its use forprotecting heating and cooking apparatus, it will be apparent to thoseskilled in the art that the novel construction embodied therein may withequal facility be utilized in connection with. other devices andapparatus.

Other objects and features of the invention will more fully appear fromthe following detailed description taken in connection with theaccompanying drawings which illustrate a single embodiment thereof, andin which:

Figure l is a View in elevation of electrical apparatus, in thisinstance an electrically heated teakettle, a portion of the side wallsthereof being cut away to disclose the manner in which the presentinvention may be embodied therein;

Figure 2 is a transverse sectional view of the teakettle showing theassociation of the present invention therewith; the section being takensubstantially on line 11-11 of Figure 1;

Figure 3 is an enlarged fragmentary view including a longitudinalsection through the safety appliance constituting the present invention,as taken substantially on line IIIIII of Figure 2;

Figure 4 is a similar view including a section through the safetyappliance, taken substantially on line IV--IV of Figure 3;

Figure 5 is a transverse sectional View showing the cooperativerelationship of the parts of the latching mechanism, taken substantiallyon line V-V of Figure 3; and

Figure 6 is an enlarged detail View in section showing the mounting ofone of the latching members and the manner in which it is anchoredagainst movement at normal temperatures.

As shown on the drawings:

Referring to Figure 1, the invention is shown as being applied to anelectrically heated apparatus, in this instance a teakettle as generallyindicated at it.

As shown, there is supported adjacent the teakettle bottom a heatingelement H of general split-ring construction, the ends of the heatingelement being supported in a base l2 secured to re tealrettle wall it.Associated with the base it and disposed outside of the tealrettle wallis a socket [4 arranged to cooperatingly receive an electric plugconnector it by means of which an electrical connection iii may be madeto the heating element.

The heating element assembly comprises insulating core H which may be ofmica other suitable material upon which there is wound a resistanceelement E8. The core with the resistance element wound thereon producesa flat construction which is laterally insulated by means of insulatingstrips of mica or other material I 9-! 9, the whole being assembledwithin a surrounding metallic sheath 20 which may be of soft copper orother suitable material.

The sheath is then laterally bent to form a split ring, the ends of thisring being supported in tubular passageways 2i and 22 which arelaterally spaced apart in a projecting boss 23 integrally formed withand extending from a hollow body portion 2-6 of the base l2. This basemay be formed of any suitable material, but is preferably formed from amaterial such as aluminum.

The hollow body portion 24 of the base is preferably of circularconstruction and terminotes at its inner portion in a peripheralmounting flange 25 which is spaced from the end of the portion 24 andarranged to be secured to the wall of the teakettle by means of suitablescrews which may threadedly engage the flange at its corners. Inmounting the base on the teakettle wall, the wall is provided with asuitable opening 25 for receiving the end portion oi the hollow baseportion 24 therethrough. In order to prevent leakage between themounting flange and the wall of the teakettle, it is preferred toprovide a gasket 21 therebetween.

The hollow base portion 24 defines a main chamber 28 into which the endsof the heatin element project. The open end of this chamber, which isslightly disposed outside the teakettle wall, is closed by the socketmember M which is preferably constructed of a suitable insulatingmaterial such as a molded plastic. This socket may be secured inposition by means of the same screws which are utilized for securing thebase l2 to the teakettle wall. On one side, the socket I4 is providedwith a peripheral flange 23 defining a recess for receiving theassociated end of the hollow portion 24 thereinto, when the flange 29issecured in abutting relation with the outer surface of the teakettlewall.

On the opposite side of the socket is a peripherally extending flange 3|which forms a plug receiving socket 32.

Suitably mounted within the socket 32 is a pair of contacts 33 adaptedto engage with contacts 34 carried by the plug, when the plug and socketare cooperatively associated by pushing one end of the plug into thesocket 32. Suitable connectors 35 extend from the heating element andconnect the ends of the heating element to the respective contacts ofthe socket.

The connections 3535 are insulatingly separated by a projection 36integrally formed with the socket M and extending into the chamber 28.The projection 35 is provided with a central passageway 31 which isslightly expanded at the end thereof which communicates with the socket32, and contracted as shown at 38, where it communicates with thechamber 28.

A plunger 39 is mounted in the contracted portion 38 for reciprocablemovement, and is provided at one end with a head 40 which is adapted toseat in the expanded end of the passage, when the plunger is pushedinwardly against the action of a spring 4| which is disposed within thepassageway surrounding the plunger, one end of this spring being inabutting relation with the head 40, and the other end of the springabutting a shoulder 42 defined by the contracted end 38 of thepassageway.

It will be noted that the spring 4| tends to move the plunger outwardlyso that the head 40 engages the innermost end of the plug connector and,if the plunger were free to move, would force the plug out of the socketand disconnect the plug and socket contacts.

This outward movement of the plunger is normally prevented by means of alatching mechanism which will now be described.

The projecting portion 23 of the base structure is provided with aninterior socket 43 which is disposed between the ends of the heatingelement and communicates at its open end with the chamber 28.

Supported within the socket 43 is a substantially U-shaped bracket 44,the legs of this bracket forming a support for the respective ends of ashaft 45. This shaft is fiatted on one side as shown at 46 to keep itfrom turning in flatted apertures 4! in the leg portions of the bracket.

The shaft rotatably supports a ratchet wheel 48 having a plurality ofperipherally formed ratchet teeth 49. This ratchet wheel is retainedagainst rotative movement on the shaft by means of a fusible material 50disposed between the interior of the wheel and shaft, the fusiblematerial preferably being a metal which will melt at a temperature ofbetween 200 F. and 300 F. It will therefore be apparent that the fusiblemetal will secure the ratchet Wheel against rotation at normaltemperatures, but if an abnormal temperature is encountered, within thelimits of the fusibility of the metal, then the metal will start to meltand permit the ratchet wheel to be rotated relative to the shaft.

The ratchet wheel forms one element of a latching mechanism andcomprises a detent in which the ratchet teeth are arranged to cooperatewith a circumferentially extending tooth 5| on a catch member 52 whichmay be secured to the adjacent end of the plunger 39 as by a threadedconnection 53.

The contracted opening 38 of the passageway through the projection 36forms a loose fit with the plunger. When the plug I5 is inserted in thesocket to connect the apparatus with a suitable electric circuit, theplug depresses the plunger and moves the tooth 5| at the inner end ofthe plunger over the inclined teeth of the ratchet wheel so that thetooth 5| will latchingly engage one of the ratchet teeth. Due to theloose fit of the plunger in opening 38, the tooth end of the plunger maydeflect sufficiently from straight line movement to permit the passageof the tooth 5| into latching position with one of the ratchet teeth.The action of spring 4| then acts to maintain the latch teeth inengagement.

With the appliance latched as just explained, the plunger will beprevented from moving outwardly to separate the plug from the socket andthus disconnect the electrical circuit from the apparatus. Thiscondition will prevail so long as the apparatus is operated at normaltemperatures. However, should the apparatus reach an abnormaltemperature, such as might occur when liquid contained in the apparatushas evaporated to such an extent as to cause overheating, the fusiblemetal will start to melt. This melting of the metal enables the ratchetwheel to turn on its supporting shaft and thus release the tooth 5| andunlatch the plunger so that it may move outwardly and disconnect theplug and receptacle. This forms a visual indication to the user of theapparatus that more liquid should be put into the apparatus, and at thesame time prevent the apparatus from overheating.

As soon as the latching tooth on the ratchet which has been effective isreleased, the movement of the plunger in rotating the ratchet Wheel willbring the next tooth into proper position for latchingly cooperatingwith the tooth 5| of the plunger, when the plunger is again depressed.Of course, as soon as the electric circuit it disconnected, theapparatus will begin cooling and the fusible metal upon cooling willagain connect the ratchet wheel against rotation on the shaft, so thatthe plunger may be again latched in safety position.

The use of a ratchet wheel having latching teeth thereon provides aplurality of latching members which are successively moved into latchingposition by the unlatching operation of the appliance.

From the foregoing description, it will be apparent that the presentinvention provides an improved safety appliance which is latched againstoperation at normal temperatures, but which will be unlatched foroperation at abnormal temperatures to disconnect the electricalconnections to the heating apparatus, and which includes a novel andimproved resetting mechanism for the latch.

The invention has been described herein more or less precisely as todetails, yet it is to be understood that the invention is not to belimited thereby, as changes may be made in the arrangement andproportion of parts, and equivalents may be substituted, withoutdeparting from the spirit and scope of the invention.

I claim as my invention:

1. In a safety appliance for electrically heated apparatus, a metallicbase adapted to support a heating element, an insulating member carriedby said base, a straight plunger bar guidingly supported in said memberfor reciprocable movement and for lateral play movement therein andhaving a tooth at its innermost end, a spring surrounding said plungerand biasing its movement in an outward direction, a toothed ratchetwheel, a horizontally disposed shaft having a flat portion on one sideonly cooperating with the bore of said wheel to define a reservoir, atooth of said wheel being engageable by the tooth of said plunger whenthe plunger is depressed against its spring, fusible means in saidreservoir normally retaining the wheel against rotation at normaltemperatures, but releasing it for rotation at abnormal temperatures,and a manually operable externally positioned circuit controllerarranged in connecting position to depress the plunger and to be movedto disconnecting position when the plunger is released relative to thewheel.

2. In a safety appliance for electrically heated apparatus having acontainer forming wall, a socket mounted in said wall, said sockethaving an end of insulating material disposed exteriorly of the wall, aflange on said end defining a recess for guidingly receiving an end of aconnection plug, a plunger guidingly supported in the socket forreciprocable movement and for lateral play movement therein, one end ofthe plunger being disposed in said recess and adapted to be depressed bythe insertion of said plug into the recess, a spring opposing depressingmovement of the plunger, and thermally controlled means in the socketfor latching the plunger in depressed position, but releasing theplunger to push the plug out of the recess when the temperature actingon said means reaches a predetermined value.

3. In a safety appliance for electrically heated apparatus, aninsulating block supported from a wall of the apparatus, a pair ofexposed spaced stationary contact members projecting outwardly from saidblock, a circuit cord connector slidably connectable with the contactmembers, a passage through the block between said contact members, anelongate plunger guidingly supported in the passage for longitudinalreciprocable movement, rotative movement and lateral play movementtherein, a spring in the block surrounding the plunger and biasing itfor movement in an outward direction, said plunger being arranged to bedepressed by the connecting movement of the circuit cord connector withthe contacts, a head portion formed at the innermost end of the plungerdefining a continuous tooth extending circumferentially of the plungerlongitudinal center line, a latch member engageable by the tooth in thedepressed position of the plunger irrespective of the position to whichthe plunger is rotated, and fusible means arranged upon melting torelease the latch member relative to said tooth, whereupon the plungeris freed for biased movement to eject and disconnect the cord connectorrelative to the stationary contacts.

ALFRED E. LANIGAN.

